Remember, “An ounce of prevention is worth a pound of cure”. THEORY OF OPERATION A block diagram of the M-2666K is shown in Figure 1. Operation centers around a custom LSI chip. This IC contains a dual slope A/D converter, display, latches, decoder and the display driver.

A/D CONVERTER A simplified circuit diagram of the analog portion of the A/D converter is shown in Figure 2. Each of the switches shown represent analog gates which are operated by the digital section of the A/D converter. Basic timing for switch operation is keyed by an external oscillator.

VOLTAGE MEASUREMENT Figure 3 shows a simplified diagram of the voltage measurement function. The input divider resistors add up 10M step being a division of 10. The divider output should be within –0.199 to +0.199V or the overload Volts 900k Common Figure 3 Simplified Voltage Measurement Diagram CURRENT MEASUREMENT...

ASSEMBLY The meter kit has been divided into a number of sections to make the assembly easy and avoid major problems with the meter operation. ONLY OPEN COMPONENT BAGS THAT ARE CALLED FOR IN YOUR ASSEMBLY PROCEDURE. DO NOT OPEN ANY OTHER BAGS. Do not build more than one section of your meter at a time.

CONSTRUCTION Introduction The most important factor in assembling your M-2666 Digital Multimeter Kit is good soldering techniques. Using the proper soldering iron is of prime importance. A small pencil type soldering iron of 25 - 40 watts is recommended. The tip of the iron must be kept clean at all times and well tinned.

IDENTIFYING RESISTOR VALUES Use the following information as a guide in properly identifying the value of resistors. PART IDENTIFICATION CARDS M-2666K To help identify the resistors and diodes used in the construction of your digital SECTION A multimeter we have mounted the diodes and resistors of each section onto a card.

RESISTOR READING EXERCISE Before starting assembly of your digital multimeter project, you should be thoroughly familiar with the 5 band color code system. Many of the resistor values will be identified by color bands and it is easy to mistake their value if you read the colors (1) yellow-black-black-black-brown (3) brown-red-violet-red-brown (5) brown-black-black-black-brown...

PARTS LIST - SECTION A If you are a student, and any parts are missing or damaged, please see instructor or bookstore. If you purchased this kit from a distributor, catalog, etc., please contact Elenco mail is at the back of this manual) for additional assistance, if needed. DO NOT contact your place of purchase as they will not be able to help you.

ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD In all of the following steps the components must be installed either on the top or bottom legend sides of the PC board as indicated. The board is turned to solder the component leads on the opposite side (installed on Bottom, soldered on Top, installed on Top, soldered on Bottom).

ASSEMBLE THE LCD Assemble the LCD into the housing with the parts shown in Figure F. Note the top of the house is curved. Wipe off zebra edges with a lint-free cloth and then insert the zebra into the top slot of the housing.

ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD In all of the following steps the components must be installed either on the top or bottom legend sides of the PC board as indicated. The board is turned to solder the component leads on the opposite side (installed on Bottom, soldered on Top, installed on Top, soldered on Bottom).

ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD Figure M Insert the IC socket into the PC board with the notch in the same direction marked on the top legend. Solder the IC socket into place. Insert the IC into the socket with the notch in the same direction as the notch on the socket.

Assembled View for Section B Attach the LCD to the PC board using the two 2.5 x 8mm screws. Use the top-mounting hole and lightly tighten the screws. Testing Procedure Capacitance 1. Place the top label over the knob and turn the range selector knob to a capacitance (C) scale position.

FINAL ASSEMBLY (continued) Feed the battery snap wires through the slot on the top case as shown in Figure U. Connect the battery and place it in the cavity of the top case as shown in Figure V. Battery Snap Wires Figure U Testing Procedure SECTION C - AC voltage and current circuit...

TROUBLESHOOTING GUIDE If the meter is not working, perform the U1 (7106) Voltage Test first. This test is to verify that the IC and Reference Voltage are operational. U1 (7106) Voltage Test 1. Measure the voltage across pin 8 and pin 34 on U1 (7106) for 9V.

REINSTALLATION OF THE RANGE SELECTOR KNOB removed rotary troubleshooting, then follow the instructions below to reinstall it. Place the PC board over the range selector knob and fasten the knob to the PC board with a M2.3 x 8 screw. CAUTION: Do not over-tighten the screw.

Transistor h Range Test Condition 2mA 3V 2mA 3V Diode Test Measures forward resistance of a semiconductor junction in k Ohm at max. test current of 1mA. 3. OPERATION 3-1 Preparation and caution before measurement 1. If the function must be switched during a measurement, always remove the test leads from the circuit being measured.

3-3 Method of Measurement (A) DC/AC Voltage Measurement 1. Connect the red test lead to “V CAP” input jack and the black one to the “COM” jack. 2. Turn the meter on by pressing the power switch. 3. Set the range selector knob to the desired volt position.

(E) Transistor h Measurement 1. The transistor must be out of circuit. Set the rotary selector knob to the h 2. Turn the meter on by pressing the power switch. 3. Plug the emitter, base and collector leads of the transistor into the correct holes in either the NPN of the PNP transistor test socket, whichever is appropriate for the transistor you are checking.